Posted: November 5, 2004

Science of Sport: Standing Tall (While Running)

The Running Research News Weekly Training Update

Hi Friends,

Recently, acquaintances have sent me several books on running form, and I was very excited to receive the volumes - since so little is known about optimizing the biomechanics of running. My excitement quickly turned to disappointment, however. Instead of providing hard data about how changes in stride length, stride rate, support time, non-support time, joint angles during support, joint angles during non-support, body-segment movements, and rear-foot motion might improve efficiency and performance, the books were actually theoretical treatises (although not identified as such by the authors), with no supporting evidence at all provided for the rather bold assertions which were made. Perhaps I am a bit of an outcast on this topic, but I would actually like to see some numbers showing that the adoption of a specific kinematic factor does indeed lead to upgraded economy and a faster 5-K time before I make an effort to change the way I run.

Before these books fell from my hands into the dustbin, however, I did notice with interest that all of them were united in one bit of "guidance": All suggested that one should run with a fairly significant forward lean of the upper body.

For the vast majority of runners, this is not exactly an earth-shaking recommendation. As you are probably aware, much of the scientific literature in this area reveals that most runners do tend to lean slightly forward throughout the gait cycle of running (ref. # 1).

Of course, this doesn't mean that the forward-lean concept is right. From various aspects of our lives, we can see that it is dangerous to argue from a general foundation of "nearly everyone does it, therefore it must be optimal." In addition, no research has ever shown that a "straight-up" runner, one who runs with virtually no forward upper-body lean, will automatically improve his/her running economy and performances by leaning forward. Indeed we can actually think of many straight-up athletes who have performed extremely well in high-level competition (list provided if requested).

What is really interesting is that the extent of lean is normally a function of both running speed and gait-cycle stage. That is (for many runners), average forward lean of the trunk tends to increase with running velocity. In addition, forward lean depends on what the stance foot is actually doing (where it's at during the gait cycle). At a pace of about 80 seconds per 400 meters, for example, forward lean at initial foot strike is often around four degrees, but at mid-support it frequently increases to 12 to 13 degrees. By toe-off, the trunk angle has often returned to approximately four degrees (2).

As you can see, the trunk and thus the low-back muscles and hip extenders are involved in a kind of whip-saw action during running. Important hip extenders such as the gluteus maximus, which originates at the top of the hip and the lower part of the back and runs down to the femur, are stretched out naturally as the trunk leans further forward in the mid-support phase of stance. The resulting, elastic snap-back of the glute maximus not only straightens the trunk back up but also helps to extend the hip and drive the body forward through toe-off. The upper back, hip area, and leg function as a kind of bow-like spring, the action of which can drive the body forward with little energy cost. Small wonder that the extent of this spring-like action (associated with greater forward lean and then a return to more-upright posture) increases with running velocity.

One might argue from this that significant forward lean at initial foot strike might actually hurt running economy, since it would thwart the operation of the spring system (it would prevent significant stretching of low-back muscles and hip extenders during stance and thus limit the extents of energy return and propulsive action). However, we have to be careful to note that no specific amount of forward lean (or lack of same) has ever been identified as optimal. We know much less about running than we should.

So what should we do? Should we make a conscious attempt to lean forward when we run? In considering this question, bear in mind that scientific studies reveal that consciously adopted changes in running form often lead to decrements rather than improvements in efficiency of movement. We can't escape the fact that we have been running in a certain way since we were about two years of age - and that our bodies have adapted to our long-used patterns; deviations from "normalcy" can make our neuromuscular systems begin to sputter. Bear in mind, too, that (for most runners) the goal of running-form changes is to improve running economy. That is, the changes we make should lower our energetic and oxygen costs of running along at particular paces and thus make it easier for us to run our races at goal speeds.

Unfortunately, there is just no way of knowing whether a form change will do that (unless you have oxygen-measuring equipment and at least four months of your life to systematically devote to the project). We can be reassured, however, by the fact that something else will almost always upgrade our efficiency of running: Strength training. A variety of different studies have shown that regular strength training can improve running economy significantly (this applies to both "standard" strength training and "explosive" work). It is very nice to know that conducting strength workouts just twice a week for a period of eight to 12 weeks will have a significantly positive impact on your running.

I would strongly argue that running-specific strength training (i. e., resistance training which mimics the biomechanics of running, putting emphasis on weight-bearing movements on one leg and on replication of specific parts of the gait cycle) would improve running economy to an even greater extent, compared with traditional strength training (the latter has been linked with upgrades of about 2 to 3 percent). However, once again we are entering the world of theory here. I hope to change that in the near future with some real research in the area.

Owen Anderson

References

(1) "Biomechanics of Running," In Exercise and Sport Sciences Reviews, Ronald L. Terjung, Ed., Volume 13, pp. 389-441, 1985
(2) "Biomechanical Effects of Fatigue on 10,000 Meter Running Technique," Research Quarterly for Exercise and Sport, Vol. 52(2), pp. 160-166, 1981

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